PHOTOISOMERIZATION AND 2ND HARMONIC-GENERATION IN DISPERSE RED ONE-DOPED AND ONE-FUNCTIONALIZED POLY(METHYL METHACRYLATE) FILMS

We have demonstrated that photoisomerization of disperse red one (DR1) dissolved in poly(methyl methacrylate) (PMMA) matrix can induce a decrease in second harmonic generation (SHG). This decrease of the SHG signal (I2omega) was measured on electric field-poled thin films of this doped polymer (guest-host system). It has an irreversible component due to irreversible disorientation of the molecules and a reversible one due to cis-trans isomerization without any orientation change of the molecules. Opposite to this case, the decay of I2omega is mainly irreversible in DR1-functionalized PMMA copolymer system studied under the same conditions. The quantum yields for trans --> cis (PHI(tc)) and cis --> trans (PHI(ct)) photoisomerization have been determined at room temperature for the doped polymer (PHI(tc) = 0.11 and PHI(ct) = 0.7), and the absorption spectrum for the thermally unstable cis form has been deduced.